Early Cretaceous Extensional‐tectonism‐related petrology of the Gan‐Hang Belt SE China: Lingshan A‐type granite at ca. 130 Ma

Abstract

A number of Late Mesozoic (ca. 130 Ma) A‐type granitic plutons have been identified in Southeast (SE) China. The Lingshan pluton, located in the Gan‐Hang Belt, is a typical one which is mainly composed of coarse‐grained biotite monzogranite in the pluton centre and medium‐ to coarse‐grained syenogranite on the margin. Zircons from three representative samples show U–Pb ages of 132.0 ± 1.3, 134.4 ± 2.1, and 133.0 ± 1.9 Ma, respectively, indicating that the Lingshan pluton were formed in the Early Cretaceous. The Lingshan granites display typical A‐type affinities, with high SiO2, K2O, Na2O + K2O, rare earth element (REE) and high field strength element (HFSE) contents, high Ga/Al and Fe# [FeOT/(FeOT + MgO)] ratios and Zr + Nb + Ce + Y contents, and apparent depletion of Ba, Sr, Ti, and Eu. The calculated zircon saturation temperatures (TZr) are high, ranging from 841 to 966 °C (mean of 886 °C). The εHf (t) values and TDM2 (Hf) of the Lingshan granites mainly vary from −3.0 to 0.2 and 1.18 to 1.38 Ga, respectively. Consistently, the εNd(t) values vary from −3.9 to −2.8 and TDM2 (Nd) range from 1.16 to 1.26 Ga. These isotopic data indicate that the Lingshan granites were likely to be generated by partial melting of Mesoproterozoic metamorphic basement rocks with the involvement of a certain amount of mantle‐derived materials. Subsequent fractional crystallization processes were also suggested during subsequent magma evolution. We propose that the ca. 130 Ma Lingshan granites together with other coetaneous A‐type granitic rocks from adjacent region indicate a back‐arc extensional setting in SE China during Early Cretaceous. The extension event might be caused by the rollback of paleo‐Pacific Plate which results in upwelling of the asthenosphere and subsequently induces a high degree partial melting of Mesoproterozoic basement sedimentary material, to generate the A‐type granitic plutons along the Gan‐Hang Belt.

Magmatic record of the Mesozoic geology of Hainan Island and its implications for the Mesozoic tectonomagmatic evolution of SE China: effects of slab geometry and dynamics in continental tectonics

“…Further to the E-NE in Jiangxi and Anhui provinces the Early Cretaceous granitoid plutons (i.e. Lingshan pluton in the Gan-Hang belt and Huayuan-gong granitoids in the Lower Yangtze River Belt) display A-type geochemical affinities with metaluminous to weakly peraluminous compositions, enriched Hf isotope ratios of zircon and a large range of high Y/Nb ratios (Yang et al 2017;Wang et al 2018). Magmas of these A-type plutons were derived from mixing of aesthenospheric melts Cretaceous volcanic rocks near the coastal regions in SE China fall into two broad time intervals.…”

“…The timing of the NW-SE-directed extension in Cathaysia has been constrained as 136-80 Ma based on thermochronological studies (Li, 2000;Zhou & Li, 2000;Li et al 2014). The results of these studies also indicate that the Cretaceous extensional tectonics and its attendant magmatism in Cathaysia migrated to the SE (oceanward in the present coordinate system) through time (Li, 2000;Li J et al 2014Li J et al , 2016Yang et al 2017;Wang et al 2018Wang et al , 2020.…”

Timing of the initiation and duration of the Cretaceous extensional regime in South‐east China: Constraints from growth strata in terrigenous basins

“…The Jinhua–Quzhou Basin is located in western Zhejiang Province (Figure 1) along the Jiangshan–Shaoxing fault belt (also named the Gan‐Hang rift belt, Li, J.H. et al., 2014b; Shu et al., 2017; Wang et al., 2018; Huang et al., 2019; Yang et al., 2021). The Early Cretaceous Qujiang Group (K 1 Q ) in this basin consists of the Zhongdai, Jinhua and Quxian formations (Figure 2B) in ascending stratigraphic order (Zhejiang BGM, 1996; Chen, 2000; Li, Y.X.…”

“…et al, 2012(Li, J.H. et al, , 2020Ji et al, 2017a;Wang et al, 2018;Suo et al, 2019;Yang et al, 2021;Xu et al, 2022), the South-eastern China Block (SECB), the focus of this article, underwent intracontinental extension, which mainly occurred during the Cretaceous (Shu et al, 2007(Shu et al, , 2009Li, J.H. et al, 2012aLi, J.H.…”

“…After a regional compression event at approximately the transition from the Jurassic to the Cretaceous (Li, J.H. et al., 2012, 2020; Ji et al., 2017a; Wang et al., 2018; Suo et al., 2019; Yang et al., 2021; Xu et al., 2022), the South‐eastern China Block (SECB), the focus of this article, underwent intracontinental extension, which mainly occurred during the Cretaceous (Shu et al., 2007, 2009; Li, J.H. et al., 2012a, 2013a, 2014a, 2014b, 2020, 2022; Li, Z. et al., 2014c; Ji et al., 2017b; Huang et al., 2019; Suo et al., 2019; Yang et al., 2012, 2021).…”